KNOCKING SOUND

2003 Honda Pilot • 120,000 miles

We have a 2003 Honda Pilot (120,000 miles). Only when it is cold outside, we hear a continuous knocking sound for around 10-15 seconds after starting the car. It then stops and does not return until the next time we start the car. It doesn't happen every single time, but it does occur most of the time. It appears to only happen when it is cold. The knocking sound seems to be coming from the console area between the two front seats. In fact, you can't hear it at all outside the car, even with the hood up. It almost sounds like it is coming from the rear of the console area, near the rear heating/cooling area. Any ideas on what this might be?